Home & Garden

How to set up a grey water system for your garden

As long as you don’t alter plumbing by cutting into pipes, you can install a grey water system without a permit.
As long as you don’t alter plumbing by cutting into pipes, you can install a grey water system without a permit.

Q: Where do I start in setting up a grey water system for my garden?

Carol, Cambria

A: Using grey water is an excellent way to reduce the waste of a valuable resource and minimize water that enters wastewater collection systems. Grey water is used household water from sinks, showers, bathtubs and washing machines. It does not include water from toilets, kitchen sinks (remember that raw chicken you rinsed), or dishwashers. Grey water should not be used on any edible plants in the garden.

While you can carry out buckets from your sink, shower or tub, there is an easier (on your back and shoulders) way to use non-potable water for outdoor irrigation. A grey water system uses gravity to redirect wastewater from a washing machine to the yard, rather than to the sewer, and is called Laundry to Landscape Grey water System.

A construction permit is not needed for this system as long as the system does not alter plumbing by cutting into pipes. A hose to the house exterior is attached to the washer hose and must follow the Health and Safety code 17922.12. This system requires a 3-way valve that allows you to switch between a grey water and sewer system. Water must be diverted to the sewer if used for dirty diapers, infectious contaminants or if it contains cleaning products harmful to plants such as bleach, softeners and dyes.

According to Chapter 16 of the California Plumbing Code, grey water cannot be stored and must be used within 24 hours from the time of collection. Immediate use minimizes the development of bacteria and other harmful pathogens.

There are other, more complicated systems than the Laundry to Landscape Grey water System. However, both require permits and plumbing alterations. It is always wise to check with San Luis Obispo County and your specific city before beginning your grey water project.

Identify detergents that are safe for the environment before using the Laundry to Landscape Grey water System. Become familiar with plants that do well with grey water such as madrone, western redbud, coffeeberry, toyon, manzanita, rosemary, ceanothus, salvia, lavender and penstemon. They will survive the alkaline environment created by grey water.

For more information on using grey water in the landscape, download Use of Graywater in Urban Landscapes in California: http://anrcatalog.ucanr.edu.

Lee Oliphant is a UCCE Master Gardener.

Got a gardening question?

In San Luis Obispo call 781-5939, Arroyo Grande, 473-7190 and Templeton, 434-4105. Visit us at http://ucanr.org/sites/mgslo/ or email us at anrmgslo@ucanr.edu. Follow us on Instagram at slo_mgs and like us on Facebook. Informative garden workshops are held the third Saturday of every month, 10 a.m. to noon at 2156 Sierra Way, San Luis Obispo. Garden docents are available after the workshop until 1 p.m. To request a tour of the garden, call 781-5939.